A rapidly growing sector of the high-technology community are companies that specialize in the design of frequently used or specific-purpose silicon IP for use in the creation of custom designed integrated circuits (IC). Such a company would have a library (or multiple libraries) of different circuits that it could license to IC designers for use in IC design. The IC designers would design whole ICs by connecting the circuits together, thus saving design time by eliminating the need to custom design the circuitry of the standard cells. For example, if the IC designers were designing an IC that features several central processing units (CPUs), phase-lock loops, counters, adders, receive and transmit circuitry, and so forth, the IC designers could simply insert circuits that performed the needed functions rather than creating the functions from scratch.
An added feature of using silicon IP is that the technology used to fabricate the IC designs can be rapidly changed when the IC fabrication technology changes. New silicon IP, wherein the circuits are designed using a new technology, can readily be used in place of existing silicon IP, wherein the circuits are designed using an older technology. The IC design can then be recompiled with the new silicon IP without requiring changes to the design of the IC.
Such flexibility places a significant value on well-designed silicon IP. Therefore, the companies that design the silicon IP do as much as they can to protect the design of their silicon IP. The companies owning the silicon IP libraries are commonly referred to as IP owners.
A commonly used technique to protect the silicon IP owner's property rights is to send to the IC designer empty models of the circuits in the silicon IP library. The empty models of the circuits are sometimes referred to as phantom views. The empty models contain only footprint descriptions and pin layouts of each of the circuit in the silicon IP library. The footprint of a circuit normally contains physical information about the circuit, such as the width and depth of the circuit along with pin information for net connections. The IC designers would then design their ICs with the phantom views and then transmit their completed design to an IC fabricator (IC fab), who may be the IP owner or has a contractual agreement with the IP owner, and therefore has access to the actual circuit designs. The phantom views used by the IC designers are then replaced by the actual circuit designs. The IC can then be verified for correctness and fabricated.
One disadvantage of the prior art is that since the phantom views only contain footprint and pin information, it is impossible for the IC designer to automatically verify the correctness of the IC's design. Rather, the IC designer must rely on the IC fab (who has access to the actual standard cells) to verify the correctness of the design. If problems are encountered, the IC fab must make the corrections, since the actual circuit designs are never provided to the IC designer.
A second disadvantage of the prior art is that since the IC fab must perform the correctness verification, it places a bottleneck at the IC fab, who may not have the manpower or equipment power to perform a thorough correctness verification on the IC. Additionally, by having the IC fab perform the correctness verification, the IC designer incurs greater costs since the IC designer cannot perform the verification in house.
A third disadvantage of the prior art is that since the IC fab performs the correctness verification, it may not be able to perform as complete a correctness verification as the IC designer would wish, therefore the probability of an improperly functioning IC may be greater than desired. The improperly functioning IC is not detectable until the actual IC is fabricated and a considerable amount of time and money is expended.